74 research outputs found
Advanced research of the impact of rotor bars anisotropic conductivity on starting torque of an induction motor with a die-cast copper cage
The paper deals with an optimal design of an induction motor with a die-cast copper cage rotor characterized by an anisotropic layer in the upper part of the rotor bars. 1D FEM optimization of an explosion-proof induction motor with a die-cast copper rotor with overall parameters of a commercial induction motor with a die-cast aluminum rotor (180 kW, 1140 V, 1500 rpm) is made with the help of numeric computations. In the paper, the design features and experimental results are given. It is shown that induction motors with a special "starting" layer placed in the upper part the diecast copper rotor bar have maximum value of starting torque for relative conductivity factors ranging from 0.3 to 0.5. The basic performance data obtained in both bench and service tests of a prototype 210kW induction motor are in close agreement with analytical data.Изложены результаты исследований влияния анизотропии проводимости стержней ротора на пусковой момент асинхронного двигателя, стендовых и эксплуатационных испытаний взрывозащищенного двигателя типа 2ЭКВ3,5-210 мощностью 210 кВт с литой анизотропной медной обмоткой ротора
Transfer of Polarized Radiation in Strongly Magnetized Plasmas and Thermal Emission from Magnetars: Effect of Vacuum Polarization
We present a theoretical study of radiative transfer in strongly magnetized
electron-ion plasmas, focusing on the effect of vacuum polarization due to
quantum electrodynamics. This study is directly relevant to thermal radiation
from the surfaces of highly magnetized neutron stars, which have been detected
in recent years. Strong-field vacuum polarization modifies the photon
propagation modes in the plasma, and induces a ``vacuum resonance'' at which a
polarized X-ray photon propagating outward in the neutron star atmosphere can
convert from a low-opacity mode to a high-opacity mode and vice versa. The
effectiveness of this mode conversion depends on the photon energy and the
atmosphere density gradient. For a wide range of field strengths, G, the vacuum resonance lies between the photospheres of
the two photon modes, and the emergent radiation spectrum from the neutron star
is significantly modified by the vacuum resonance. (For lower field strengths,
only the polarization spectrum is affected.) Under certain conditions, which
depend on the field strength, photon energy and propagation direction, the
vacuum resonance is accompanied by the phenomenon of mode collapse (at which
the two photon modes become degenerate) and the breakdown of Faraday
depolarization. Thus, the widely used description of radiative transfer based
on photon modes is not adequate to treat the vacuum polarization effect
rigorously. We study the evolution of polarized X-rays across the vacuum
resonance and derive the transfer equation for the photon intensity matrix
(Stokes parameters), taking into account the effect of birefringence of the
plasma-vacuum medium, free-free absorption, and scatterings by electrons and
ions.Comment: 19 pages with 9 figures; minor additions (mainly the at end of
sec.5.2); ApJ in press (v588, n2, May 10, 2003 issue
On the Internal Structure of Relativistic Jets
A magnetohydrodynamic model is constructed for a cylindrical jet immersed in
an external uniform magnetic field. It is shown that, as in the force-free
case, the total electric current within the jet can be zero. The particle
energetics and the magnetic field structure are determined in a self-consistent
way; all jet parameters depend on the physical conditions in the external
medium. In particular, we show that a region with subsonic flow can exist in
the central jet regions. In actual relativistic jets, most of the energy is
transferred by the electromagnetic field only when the magnetization parameter
is sufficiently large, . We also show that, in general, the
well-known solution with a central core, ,
can not be realized in the presence of an external medium.Comment: 19 pages, 2 figure
Properties of the noise storm source at wavelength 1 m from observations of the solar eclipse on March 29, 2006
On the Possibility of Generating Harmonics of the Electron Plasma Frequency in the Solar Atmosphere due to Explosive Instability in a System of Interpenetrating Electron and Ion Flows
On the criterion for effectiveness of wave linear transformation in a smoothly inhomogeneous medium and of nonadiabatic transitions during atomic collisions
The use of a neural network in solving problems of recognition and classification of spacecraft by their optical images
In recent years, the number of space objects located in near-Earth outer space, especially in the near operational zone, has increased significantly due to the build-up of space groupings, including dual-use (for example, Starlink) and the remnants of their vital activity (space debris). This factor increases the importance of the task of recognizing and classifying space objects by type in the shortest possible time and entering them into the main catalog of space objects. The developed methodology allows automated analysis of optical images of space objects using software to solve the problem of their recognition and classification by type using a convolutional neural network. The purpose of the study is to increase the efficiency of processing and analysis of optical images of spacecraft. The experimental results of the study confirm the achievement of the research goal. The developed methodology contributes to the development of software and hardware for image processing and can be used in calculations and data preparation for information support of interested officials. For the first time, a training set for a convolutional neural network has been prepared using real optical images of spacecraft obtained in the visible range
Observation in Crimea of solar eclipse on August 1, 2008, at wavelengths 10.5 and 12 cm in the epoch of minimum of solar activity
- …